This invention relates to a shifting device for an outboard drive unit and more particularly to an improved shifting device incorporating a hydraulically operated clutch.
As is well known, many forms of outboard drive units employ forward, neutral, reverse transmissions. Such transmissions are common in both outboard motors and in the outboard drive unit of an inboard-outboard drive. Typically, such a transmission includes a driving bevel gear and a pair of oppositely rotating driven bevel gears that are journaled on a shaft. A dog clutching mechanism is provided for selectively coupling selected ones of the driven bevel gears to the shaft for either forward, neutral or reverse drive. Although such mechanisms have the obvious advantage of simplicity, there are a number of disadvantages to the use of dog clutches. Such clutches are difficult to engage and are also noisy in their operation. This is particularly true when attempts are made to shift the dog clutching element when they are rotating at high speeds. However, the dog clutch mechanism has a particularly advantage in that it is able to effectively transmit high degrees of power.
In connection with inboard-outboard drives, it has been proposed to employ a separate clutch for driving the forward, reverse transmission. By employing such a separate clutch, it is possible to facilitate shifting and the clutch may be of the friction type and can, if desired, be hydraulically operated. However, it has been the conventional practice to mount such clutches directly between the engine and a shaft which extends from the engine through the transom of the watercraft to the remotely positioned outboard drive. As a result, there is a certain degree of complexity in the resulting operation. Furthermore, if some form of interlock is provided between the frictional clutch and the dog clutch of the forward, reverse transmission, the construction obviously becomes very complicated due to the remote positioning of the two transmissions and the fact that they are carried by completely different units of the mechanism.
It is, therefore, a principal object of this invention to provide an outboard drive arrangement that has a separate selectively engageable friction clutch and a forward, reverse transmission both of which are contained within a common housing of the outboard drive.
It is a further object of this invention to provide an improved transmission mechanism for an outboard drive wherein the clutching and shifting arrangements are isolated from each other.
It is a still further object of this invention to provide a simple and yet effective separate transmission and clutching mechanism for a marine outboard drive all contained within a common housing.
It is advantageous to use hydraulic actuations for the clutch of a marine transmission is obvious. The hydraulic mechanism itself tends to smoothen the shifting operation. However, the addition of a further and external pump for operating the clutch as heretofore proposed has obviously complicated the arrangement.
It is, therefore, a further object of this invention to provide an improved and simplified hydraulic clutch actuating mechanism for a marine outboard drive.